ULP Wireless Update

 Finger tip-sized wireless module boasts Arduino compatibility


Open Source RF’s finger tip-sized, plug-and-play board is based on familiar Arduino hardware and software but with the added capability of ULP wireless


RFduino adds wireless for smartphone connectivity to the popular Arduino microcontroller board, opening up the possibility of thousands of new applications

For the last 30 years, Armen Kazanchian, Founder and President of RF Digital Corp., a Californian RF engineering specialist, has been busy helping commercial concerns solve their RF engineering challenges and supplying a wide range of highly-optimised RF modules. However, Kazanchian’s latest product is in support of his hobby. This time he’s focusing on the ‘maker movement’ – the growing band of amateurs that delve into the world of electronics as a hobby.


Three factors have kindled Kazanchian’s interest in developing the product. The first is Arduino, a microcontroller board born in the Interaction Design Institute in the city of Ivrea, Italy, in 2005. Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware and software. It’s intended for artists, designers, hobbyists, and anyone interested in creating interactive objects or environments.


According to the Wall Street Journal, in the space of an hour, a layman can make Arduino blink an LED, run a motor or send a temperature reading to a computer monitor. And with a little practice, people have been able to do much more.


“I wanted to make a substantial contribution to the maker community and at the same time support Arduino, my favourite hobby-amateur project environment,” says Kazanchian


The second factor driving Kazanchian’s latest venture is the recent incorporation of chips and software supporting Bluetooth v4.0 wireless technology into the latest generation of smartphones and tablet PCs. This capability allows such devices to wirelessly connect with compact products, powered by coin cell batteries, such as handset accessories, sports & fitness monitors, and toys.


The final factor which grabbed his attention was the introduction of Nordic Semiconductor’s nRF51822 Bluetooth low energy and 2.4GHz proprietary System-on-Chip (SoC). RF Digital has been working with Nordic for many years and has produced a range of RF modules based on the nRF24L Series proprietary transceivers, and its latest release is the RFD51822. This module provided the foundation for enabling Arduino compatibility.


Bluetooth made simple

“We’ve come up with a mini-sized, plug-and-play board based on familiar Arduino hardware and software but with the added capability of RF Digital’s professional Bluetooth low energy wireless module incorporating Nordic’s nRF51822 SoC. It’s called RFduino,” explains Kazanchian.


“This product is particularly exciting for me because it helps makers connect their projects to an Apple iPhone, iPad, Android smartphone or tablet using a single self-contained mini-sized unit which runs Arduino code. RFduino can support a range of applications that’s impossible to imagine.”


According to Kazanchian, RFduino is similar to the Arduino UNO or DUE, except that it’s a fraction of the cost and size and has wireless connectivity built-in. Until RFduino, adding wireless to an Arduino required an additional wireless ‘shield’— a plug-in board—which increased cost and size. Better yet, RFduino uses the nRF51822 SoC’s 32-bit ARM Cortex-M0 processor, which is far more powerful than the microprocessor in the Arduino UNO. However the ARM device still runs the same, simple Arduino code of the UNO.


RFduino also uses Arduino’s IDE. By employing this IDE and a small sized USB shield, RFduino can be plugged into a PC USB port and the user can download any of the thousands of applications (‘sketches’) already written by the Arduino community directly onto the device with minimal adjustments. The software then automatically begins running on the RFduino. Alternatively, a user can create their own custom sketch and download it to the device.


RFduino uses the DIP form factor with 0.1-in (2.54mm) pins, so it easily plugs directly into the solderless breadboards favored by hobbyists. After detaching the RFduino USB shield, the device is ready to power the hobbyist’s project and seamlessly connect with a smartphone. Kazanchian cites the example of a smartphone communicating with an RF module that controls a relay connected to a motor operating window blinds as just one of the applications a hobbyist can easily create.


Open Source RF, a company started by Kazanchian in support of hobbyists, has entered in to the open source spirit by making smartphone applications, hardware files for shields, and source code available from its own RFduino application examples. These include wireless multi-color RGB LED lighting, smartphone controlled racing cars, temperature sensors, house plant watering sensors, proximity and motion sensors, relay switches, and audio controls among others.


Hiding the complexity

Kazanchian’s company has taken the complex technology of Nordic’s nRF51822 SoC and made it accessible to anyone familiar with the Arduino Integrated Development Environment (IDE). Specifically, RFduino uses RF Digital’s RFD51822 module—a highly-optimised radio device—and its API which enabled Open Source RF to integrate the Arduino environment and radio into a single device. The end result is a product that allows amateurs to come up with coin cell-powered wireless accessories that can link to a smartphone.


The key to the trick is the nRF51 Series’ unique architecture combined with RF Digital’s module and API. The SoC is supplied complete with a verified and qualified Bluetooth low energy “Soft Device” separated from the SoCs application code area. This allows a developer to rapidly create novel applications safe in the knowledge that the RF protocol software can’t be corrupted and is already Bluetooth v4.0- and RF-approved. Other solutions don’t separate the protocol software and application code in this way - making life complicated for a professional to handle the inevitable run-time dependencies that arise and putting the devices out of the reach of the amateur.


The Bluetooth low energy stack in the nRF51822 is protected so the amateur doesn’t have to worry about damaging it. Better yet, RF Digital has made life even simpler by creating a special layer of software that sits between the nRF51822’s application code area and the Soft Device. This “API and bootloader” is what makes the task of downloading Arduino code onto RFduino possible.


“The RFduino connects to RF Digital’s API and bootloader and provides a direct interface to the Arduino IDE, hiding away complexity while enabling the user access to low level functionality,” says Kazanchian. “All the intricacy typically surrounding Bluetooth low energy has been ‘abstracted away’ with RFduino commands which are simple enough for the beginner while allowing flexibility for advanced users to make the module do just what they need.”


Kazanchian has set up a wireless start-up venture called Open Source RF––launched on KickStarter.com––to sell RFduino to the public.


“I introduced the RFduino on KickStarter.com, because it’s a forum for creativity and innovation,” notes Kazanchian, “It brings me great pleasure to know that I am participating in bringing advanced wireless technology to the amateur world and helping bridge the gap between complex smartphone connectivity and thousands of makers like myself who are driven by a genuine passion for electronics.”